Such a mechanism is generally of the kind that comprises a crank coupled with a motor shaft and having a crank pin mounted on the crank towards the end of the crank away from the motor shaft with a crank head piece mounted eccentrically on the crank pin and a crosshead pivoted on the crank head piece. The crank head piece incorporates a latch which comprises a latch finger movable in a direction substantially parallel to the axis of the crank pin under the action of resilient means. The mechanism includes selective coupling means including the latch, which acts in such a way as to leave the crank head piece uncoupled from the crank when the latter is rotating in a first direction, but to prevent relative movement between the head piece and the crank when the latter is rotating in the opposite direction. Stop means are also provided for coupling the crosshead and crank head piece for rotation together when the crank is rotating in the first direction.
In normal wiping operation of the mechanism defined above, the crank rotates in one direction for which the position of the eccentric head piece remains constant with respect to one of the other elements, namely the crosshead or the crank, while when the direction of crank rotation is reversed there is, instead, relative rotation between the head piece and that other element. This causes the eccentricity to change, which results in the wiper blade or blades being retracted into the parking state. Such a mechanism will be referred to as a mechanism of the kind specified.
It is known that with such a drive mechanism when the wiper assembly is not in use, with the wiper blade in the park position the blade lies below the visible edge of the bodywork in the vicinity of the glass. This enables the whole of the glass to be available to be seen through by the driver. Furthermore, from the aesthetic point of view, the windshield wiper is no longer visible above the line of the bodywork.
Hitherto various arrangements have been proposed for practical embodiments of such a drive mechanism which enable a windshield wiper or set of wipers to be moved into a park position. There is a need to improve these arrangements in terms both of their construction and of their operation.